Optical member and method for producing same

ABSTRACT

The present invention is directed to an optical member including: a first layer that includes a first region having a refractive index n1 and a second region having a refractive index n3; and a second layer disposed on a first main surface of the first layer so as to be in contact with the first region and the second region, the second layer having a refractive index n2. The first layer includes a plurality of said second regions adjoining the first region along a planar direction of the first layer; the plurality of second regions constitute a geometric pattern; and n1 to n3 satisfy the relationship n1&lt;n3&lt;n2. When an optical member according to the present invention is integrated with a lightguide in use, excellent light extraction function is exhibited and leakage of light due to light scattering is suppressed, while attaining good mechanical strength at the same time.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/982,251, filed Sep. 18, 2020, which is a National Stage Entry ofInternational Patent Application No. PCT/JP2019/012029, filed Mar. 22,2019, which claims priority to U.S. Provisional Application No.62/646,461, filed Mar. 22, 2018. The disclosures of each of theapplications listed above are incorporated by references herein in theirentireties.

TECHNICAL FIELD

The present invention relates to an optical member for use inillumination devices, image displaying devices, and the like. Moreparticularly, the present invention relates to an optical member which,when integrated with a lightguide, is able to selectively extract lightfrom the lightguide.

BACKGROUND ART

In order to extract light from a lightguide, a lightguide havingconcave-convex shapes formed on the surface thereof has conventionallybeen used. In making a lightguide having such concave-convex shapes onthe surface, according to the purpose and dimensions, it is necessary tomake a mold of the concave-convex shapes each time. In such a lightguidehaving concave and convex parts, while the presence of air in contactwith the concave-convex shapes plays a geometrically important role forlight extraction, the lightguide is difficult to be made thin orlaminated with other members. Furthermore, as the concave-convex shapesneed to be made more precise and complex for realizing multiplefunctions, the production of lightguides is becoming time-consuming andcostly, among other problems.

On the other hand, Patent Document 1 proposes that: avariable-refractive index light extraction layer having a geometricarrangement of two regions of different refractive indices be made; and,when it is integrated with a lightguide, light be selectively extractedfrom the lightguide.

CITATION LIST Patent Literature

Patent Document 1: Japanese National Phase PCT Laid-Open Publication No.2015-534100

SUMMARY OF INVENTION Technical Problem

The inventors have studied Patent Document 1, and found that the threepoints as detailed below need to be improved.

Firstly, as shown in FIG. 1, the light extraction layer disclosed inPatent Document 1 includes low-refractive index layers 1 and ahigh-refractive index layer 2 disposed along the planar direction of thelight extraction layer, such that an interface exists at which regionsof considerably different refractive indices adjoin, and therefore lightscattering due to reflection or refraction at the interface occurs,possibly causing leakage of light.

Secondly, according to the method of producing a light extraction layerdisclosed in Patent Document 1, as shown in FIG. 2, the spaces betweenregions of low refractive index (first region; low-refractive indexlayers 1) are not sufficiently filled with a second region(high-refractive index layer 2) having a higher refractive index thanthat of the first region, thus leaving air layers 3, so that not only isthere a risk of light scattering, but there is also a risk ofinsufficient mechanical strength due to the light extraction layer notbeing sufficiently bonded to the lightguide.

Thirdly, since regions of low refractive index inherently include porousstructures, regions of low-refractive index are very brittle anddifficult to handle. In addition, there are extreme manufacturingdifficulties in creating partial coatings of low refractive indexregions on a support substrate.

A problem to be solved by the present invention is to provide an opticalmember which suffers little light scattering and achieves excellentmechanical strength when being integrated with a lightguide, the opticalmember enabling selective extraction of light, and a method of easilyproducing such an optical member.

Solution to Problem

The present invention has been made in view of the above problem, andsummary of the present invention is as follows.

An optical member comprising:

-   -   a first layer that includes a first region having a refractive        index n₁ and a second region having a refractive index n₃; and    -   a second layer disposed on a first main surface of the first        layer so as to be in contact with the first region and the        second region, the second layer having a refractive index n₂,        wherein,    -   the first layer includes a plurality of said second regions        adjoining the first region along a planar direction of the first        layer;    -   the plurality of second regions constitute a geometric pattern;        and    -   n₁ to n₃ satisfy inequality (1) below.

n₁<n₃<n₂   (1)

Advantageous Effects of Invention

According to the present invention, when an optical member according tothe present invention is integrated with a lightguide in use, an effectis provided in that excellent light extraction function is exhibited andleakage of light due to light scattering is suppressed, while goodmechanical strength is attained at the same time.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A cross-sectional view of a conventional light extraction layer

FIG. 2 A cross-sectional view of a light extraction layer obtained byfollowing a conventional method of preparing a light extraction layer

FIG. 3 A cross-sectional view of a light distribution element obtainedby using an optical member according to the present invention

FIG. 4 A diagram showing light guiding by a light distribution element

FIG. 5 A cross-sectional view of an optical member according to thepresent invention

FIG. 6 A plan view of a first layer having stripe shapes of a pluralityof second regions

FIG. 7 A plan view of a first layer having a plurality of circularsecond regions

FIG. 8 A cross-sectional view showing another form of a lightdistribution element

FIG. 9 A cross-sectional view showing another form of a lightdistribution element

FIG. 10 A cross-sectional view showing another form of a lightdistribution element

FIG. 11 A conceptual diagram of forming second regions through laserirradiation

FIG. 12 A conceptual diagram of forming second regions via ink-jet

FIG. 13 A conceptual diagram of preparing a light extraction layerhaving cavities (a member having an air cavity structure to achievelight outcoupling)

FIG. 14 A micrograph showing that a portion of a geometric pattern of aphotocurable resin monomer has been formed on a pressure-sensitiveadhesive layer via ink-jet

FIG. 15 A calculation model corresponding to Example 1, for use incalculation

FIG. 16 A calculation model corresponding to Comparative Example 1, foruse in calculation

FIG. 17 A graph snowing calculation results of a quantity of lightleaking from rear surface in each calculation model

DESCRIPTION OF EMBODIMENTS

The present invention is directed to an optical, member, including: afirst layer that includes a first region having a refractive index n₁and a second region having a refractive index n₃; and a second layerdisposed on a first main surface of the first layer so as to be incontact with the first region and the second region, the second layerhaving a refractive index n₂. The first layer includes a plurality ofsaid second regions adjoining the first region along a planar directionof the first layer; the plurality of second regions constitute ageometric pattern; and n₁ to n₃ satisfy inequality (1) below.

n₁<n₃<n₂   (1)

When an optical member according to the present invention is integratedwith a lightguide in use, excellent light extraction function isexhibited and leakage of light due to light scattering is suppressed,while attaining good mechanical strength at the same time.

Hereinafter, the present invention will be described in detail; however,the present invention is not limited to the following embodiments, butmay be carried out in some modified forms.

1. Light Distribution Element

First, in order to describe the significance of the optical memberaccording to the present invention, a light distribution element whichis obtained by integrating the optical member according to the presentinvention with a lightguide will be described.

FIG. 3 is a cross-sectional view of an example of employing an opticalmember 300 according to an embodiment, where the optical member 300 isintegrated with a lightguide 4 into a light distribution element, thelight distribution element being intended to extract light upwards. InFIG. 3, on a first main surface 11 of a first layer 100, a second layer200 is provided via a first main surface 21 of the second layer, thesecond layer 200 being in contact with a first region 101 and secondregions 102 of the first layer 100 via the first main surface 21 of thesecond layer. Moreover, the lightguide 4 is disposed in contact with asecond main surface 12 of the first layer 100 via a first main surface41 of the lightguide 4. As will be described later, the refractive indexof the lightguide preferably has a value in the range from −0.1 to +0.1relative to the refractive index n₂ of the second layer. In FIG. 3,where the transverse direction in the cross section defines an x axisand the vertical direction in the cross section defines a y axis, thefirst layer 100 includes the first region 101 and the second regions 102along the x axis direction, i.e., along the planar direction of thefirst layer 100. Herein, on the second main surface 42 of the lightguide4, an air layer (refractive index 1.00) or a light-reflective element orlight-scattering element is disposed (not shown).

In the light distribution element of FIG. 3, when light is allowed toenter the lightguide 4 from a light source 5, as shown in FIG. 4, lightis reflected by the second main surface 42 of the lightguide 4, andguided in the lightguide 4 from left to right in the figure, whilereflecting at the first region 101. The light which is guided withrepetitive reflections travels through a second region 102 without beingreflected, whereby the light is extracted above the light distributionelement (out-coupling).

In other words, with the optical member according to the presentinvention, light can be extracted only from the second regions;therefore, by adjusting a geometric pattern that is created by the firstregion and the second regions, it becomes possible to extract light fromonly the desired portions. As a result, desired light extractioncharacteristics can be realized according to the purpose.

Lightguide

The lightguide may typically be composed of a film or plate-like memberof resin (preferably a transparent resin). Typical examples of suchresins include thermoplastic resins and reactive resins (e.g., ionizingradiation-curable resins). Specific examples of thermoplastic resinsinclude (meth)acrylic resins such as polymethyl methacrylate (PMMA) andpolyacrylonitrile, polycarbonate (PC) resins, polyester resins such asPET, cellulose-based resins such as triacetyl cellulose (TAC), cyclicpolyolefin-based resins, and styrene-based resins. Specific examples ofionizing radiation-curable resins include epoxy acrylate-based resinsand urethane acrylate-based resins. These resins may each be used aloneby itself, or any two or more of them may be used in combination.

The thickness of the lightguide may be e.g. 100 μm to 100 mm. Thethickness of the lightguide is preferably 50 mm or less, more preferably30 mm or less, and still more preferably 10 mm or less.

The refractive index of the lightguide usually has a value in the rangefrom −0.1 to +0.1 relative to the refractive index n₂, and its lowerlimit value is preferably 1.43 or more, and more preferably 1.47 ormore. On the other hand, the upper limit value of the lightguide is 1.7.Although some examples of the refractive index of the lightguide aregiven here, in the case where the first region is disposed directly incontact, with the lightguide, the refractive index of the lightguide maybe designed so that light is reflected by the first region; or, in thecase where the first region is disposed on the lightguide via the secondlayer, the refractive index of the lightguide may be designed by takingthe refractive index of the second layer into account so that light isreflected by the first region.

A lightguide to be used in conjunction with an optical member accordingto the present invention to provide a light distribution element may bea conventional lightguide having concave-convex shapes or the like,e.g., a lightguide which lacks any optical pattern such as a lightout-coupling pattern. This novel light distribution element, into whicha non-patterned lightguide and an optical member according to thepresent invention are integrated, provides illumination on a target suchas a display surface, for example, typically by boundaryinterface/surface lamination. This boundary interface lamination allowslight to pass and strike a target surface such as a display surface, forexample, for illumination or light displaying purposes. Moreover, inorder to manipulate the passage and direction of light, the boundaryinterfaces on both sides may be laminated and controlled throughrefractive index matching.

A light distribution element into which an optical member according tothe present invention and the aforementioned non-patterned lightguideare integrated provides an advantage in terms of efficiency infrontlight solutions. The efficiency relies on the refractive index ofthe light-guiding medium, and the refractive indices of the layers to bebonded or laminated, claddings, and coatings. In this novel solution, inwhich the lightguide lacks an optical pattern, minimizes stray light andalso improves contrast and efficiency with an enhanced transparency.

Moreover, an optical member according to the present invention, whenintegrated with a non-patterned lightguide into a light distributionelement, can realize an excellent light extraction function even withoutany concave-convex shapes for light out-coupling (light extraction) onthe lightguide.

2. Optical Member 2-A. First Layer

An optical member according to the present invention includes a firstlayer that includes a first region having a refractive index n₁ andsecond regions having a refractive index n₃. With a first layer of suchconfiguration, as described in detail in <1. Light distribution element>above, the light extraction function of the light distribution elementis achieved. FIG. 5 shows an example of a cross-section of an opticalmember 300 according to the present invention, where a geometric patterns formed in the first layer 100 from the aforementioned first region 101and second red ions 102. Examples of the geometric pattern includegeometric patterns shown in FIG. 6 and FIG. 7. As shown in the planviews of FIG. 6 and FIG. 7, the first region 101 and the second regions102 are disposed so as to be contiguous with one another, thusconstituting the first main surface 11 and the second main surface 12(see FIG. 3) of the first layer 100. In FIG. 6, in a plane that isdefined by the first region 101, a plurality of second regions 102 areformed in stripe shapes. When an optical member according to the presentinvention is integrated with a lightguide into a light distributionelement in use, the geometric pattern created by the plurality of secondregions is formed so that the second regions 102 are first sparse andlater become denser, based on the position of the light source 5 (e.g.,an LED) that is attached to an end of the lightguide.

The thickness of the first layer is not particularly limited so long asthe light extraction function is realized; however, usually, its lowerlimit value may at least be greater than the wavelength of the incidentlight. Specifically, the lower unit value is 0.3 μm or more. On theother hand, although not particularly limited, its upper limit value isusually 5 μm or less, and more preferably 3 μm or less. So long as thethickness of the first layer is within the aforementioned range, theconcave and convex parts of the surface of the light distributionelement will not be large enough to affect lamination, so that very easycombination or lamination with other members can be attained.

2-B. First Region

In the present invention, the first region has a refractive index n₁.Although the first region may be composed of any suitable materialwithout being particularly limited, it is preferably formed so that n₁is 1.2 or less. The upper limit of n₁ is usually 1.2 or less, preferably1.18 or less, and more preferably 1.15 or less. On the other hand, thelower limit of n1 is not particularly limited, but is preferably 1.05 ormore from the standpoint of mechanical strength.

Moreover, in the present invention, the first region may have a porestructure. For example, the pore structure of the first region has oneor more kinds of structural units forming a fine pore structure, whereinthe structural units are chemically bonded to one another throughcatalytic action. Thus, in a structure in which the micropore structuralunits are chemically bonded to one another through catalytic action,since it is not a conventional pore structure whose main component is abinder resin used as the matrix, not only can the refractive index (n₁)be made a low refractive index of 1.2 or less, but also the strength ofthe pore structure itself can be increased. Example shapes of theaforementioned micropore structural unit include particle, fiber, rod,and flat plate shapes. The structural unit may have only one shape, ormay have a combination of two or more shapes.

The lower limit value of the porosity of the first region is usually 40%or more, preferably 50% or more, and more preferably 55% or more. On theother hand, its upper limit value is usually 90% or less, and morepreferably 85% or less. By keeping the porosity within the above range,the refractive index of the first region can be set in an appropriaterange.

An example of a method of measuring the porosity will be described. Ifthe layer of which porosity is to be measured single layer and onlycontains pores, the rate of air to the substance composing the layer(volume ratio) can be calculated by a usual method (e.g. by measuringweight and volume and calculating the density), whereby the porosity(vol %) can be calculated. Since the refractive index and the porosityare correlated, for example, the porosity can be calculated from thevalue of the refractive index of a layer. Specifically, for example, theporosity is calculated from the value of the refractive index asmeasured by an eilipsometer from Lorentz-Lorenz's formula.

The film density of the first region is e.g. 1 g/cm³ more, preferably 10g/cm³ or more, and more preferably 15 g/cm³ or more. On the other hand,the film density is e.g. 50 g/cm³ or less, preferably 40 g/cm³ or less,more preferably 30 g/cm³ or less, and still more preferably 2.1 g/cm³ orless. The range of film density e.g. 5 g/cm³ to 50 g/cm³, preferably 10g/cm³ to 40 g/cm³, and more preferably 15 g/cm³ to 30 g/cm³.Alternatively, the range is e.g. 1 g/cm³ to 2.1 g/cm³. The porositybased on the film density of the first region is e.g. 50% or more,preferably 70% or more, and more preferably 85% or more. On the otherhand, the porosity based on film density is e.g. 90% or less, andpreferably 85% or less.

The film density can be measured by the following method, for example;in another approach, the porosity can be calculated in the followingmanner based on the film density, for example.

After the first region is formed on the substrate material (acrylicfilm), regarding the pore regions in this laminate body, an X-rayreflectivity in the total reflection region is measured by using anX-ray diffraction apparatus (RINT-2000: manufactured by RIGAKUCorporation). Then, after fitting the intensity and 2θ, the film density(g/cm³) is calculated from a total reflection critical angle of thelaminate body (first region/substrate material), and furthermore aporosity (P%) is calculated from the following equation.

porosity (P%)=45.48×film density (g/cm³)+100(%)

It is supposed that the size of pores (voids) in the first region refersto, between the diameter along the major axis and the diameter along theminor axis of each pore (void), their diameter along the major axis. Thesize of pores (voids) is e.g. 2 mm to 500 nm. The size of pores (voids)is e.g. 2 nm or more, preferably 5 nm or more, more preferably 10 nm ormore, and still more preferably 20 nm or more. On the other hand, thesize of pores (voids) is e.g. 500 nm or less, preferably 200 nm or less,and more preferably 100 nm or less. The size range of pores (voids) ise.g. 2 nm to 500 nm, preferably 5 nm to 500 nm, more preferably 10 nm to200 nm, and still more preferably 20 mm to 100 nm. The size of pores(voids) can be adjusted to a desired size, depending on the purpose,application, etc.

The size of the pores (voids) can be quantified by the BET test method.Specifically, 0.1 g of a sample (the formed pore layer) is fed into thecapillary of a specific surface area measurement apparatus (ASAP2020:manufactured by Micromeritic), and then the sample is subjected tovacuum drying at room temperature for 24 hours to degas the interior ofthe pore structure of gases. Then, by allowing nitrogen gas to beadsorbed to the above sample, adsorption isotherms are drawn to obtain apore distribution. Thus, the pore size can be evaluated.

Examples of the first region having a pore structure include a firstregion having porous regions and/or air regions. The porous layertypically includes aerogel and/or particles (e.g., hollow microparticlesand/or porous particles). The first region may preferably be ananoporous layer (specifically, a porous layer 90% or more of whosemicropores have a diameter in the range from 10⁻¹ nm to 10³ nm).

Any suitable particle can be adopted as the aforementioned particles.The particles typically are composed of a silica-based compound.Examples of the shape of the particles include sphere, plate, needle,string, and grape cluster shapes. Examples of string-shaped particlesinclude for example: a plurality of particles having a sphere, plate, orneedle shape connected into a beadroll; short fiber-like particles(e.g., short fiber-like particles described in Japanese Laid-Open PatentPublication No. 2001-188104); and combinations thereof. The string-likeparticles may be linear-chained or branched. Examples of grape clustersof particles include, for example, a plurality of sphere-, plate-, orneedle-shaped particles aggregating into a grape cluster. The shape ofthe particles can be confirmed, for example, by observing them under atransmission electron microscope. The average particle size of theparticle is e.g. 5 nm to 200 nm, and preferably 10 nm to 200 nm. Withthe above configuration, a first region with a sufficiently lowrefractive index can be obtained, and the transparency of the firstregion can be maintained. In the present specification, the averageparticle size means a value derived, from a specific surface area (m²/g)measured by the nitrogen adsorption method (BET method), by the formula:average particle else=(2720/specific surface) (see Japanese Laid-OpenPatent Publication No. 1-317115).

Specific examples of the method of forming the first region according tothe present invention will be described in detail at <3. Method ofproducing optical member>.

2-C. Second Regions

In the present invention, the second regions have a refractive index n₃.n₃ satisfies the relationship n₁<n₃<n₂. Since n₃ satisfies the aboverelationship, light scattering due to reflection and refraction atinterfaces between the first region and the second regions along theplanar direction of the first layer can be prevented, and leakage oflight can be suppressed. Although the second regions may be composed ofany suitable material without being particularly limited, it ispreferably formed so that n₃ is not less than 1.25 and not more than1.4. The lower limit value of n₃ is usually 1.25 or more, preferably1.30 or more, and more preferably 1.35 or more from the standpoint oflight extraction function. On the other hand, its upper limit value is1.4 or less from the standpoint of suppressing leakage of light. Thesecond regions may be designed optically by taking into account thefirst layer excluding the second regions and the second layer so that,when made into a light distribution element it allows light to betransmitted.

For example, the second regions contain: a substance forming the samepore structure as that of the first region; and a resin or othersubstance. The refractive index (n₃) of the second regions is calculatedbased on the refractive index and volume fraction of the materialcomposing the first region, the refractive index and volume fraction ofair in the pores that are not filled with the resin or the like, and therefractive index and volume fraction of the resin or the like.

In another aspect, the second regions have a skeleton of the same porestructure as that of the first region, and are formed by filling thepores in the pore structure with a resin or other substance. The fillfactor of the pores in the second regions is not particularly limited,so long as the fill factor allows the refractive index n₃ to be not lessthan 1.25 and not more than 1.4. Theoretically, when the fill factor is0%, the refractive index of the second regions is equal to therefractive index of the first region; and when the fill factor 100%, therefractive index of the second regions is to be calculated based on therefractive index and volume fraction of the material composing the porestructure and the refractive index and volume fraction of the resin orother substance used for filling, and has a value smaller than n₂.

In another aspect, the second regions are formed to contain: a substancecomposing the first region; and resin A (described later), which iscontained in the second layer. Resin A may be the resin A that isderived from the second layer, or a resin A that is provided separatelyof the second layer formation. Specifically, the second regions areobtained as resin A fills the pore structure that is formed by thesubstance composing the first region. Resin A will be described indetail at (2-D. second layer) below.

In another aspect, the second regions are formed to contain: a substancecomposing the first region; and resin B. Specifically, the secondregions are obtained as resin B fills the pore structure that is formedby the substance composing the first region. Examples of resin Bcontained in the second regions include pressure-sensitive adhesives andenergy active ray-curable resins.

Pressure-sensitive adhesive b to be used as resin B is preferably softenough to be able to permeate the pores in the first region underheating conditions, e.g., the aging step to be described later, forexample. Specifically, pressure-sensitive adhesive b has a storagemodulus of elasticity of preferably 9.0×10⁴ (Pa) or less, and morepreferably 5.0×10³ (Pa) to 8.5×10⁴ (Pa). As the aforementionedpressure-sensitive adhesive b, any appropriate pressure-sensitiveadhesive may be used so long as it has such characteristics. Examples ofthe pressure-sensitive adhesive typically include acrylicpressure-sensitive adhesives (acrylic pressure-sensitive adhesivecompositions). Acrylic pressure-sensitive adhesive compositions will bedescribed in (2-D. second layer) below. However, the pressure-sensitiveadhesive b preferably does not include a heterocyclic-ring containing(meth)acrylate as a comonomer. Details of the acrylic pressure-sensitiveadhesive composition composing pressure-sensitive adhesive B aredescribed in, for example, Japanese Laid-Open Patent Publication No.2016-190996, the disclosure of which is incorporated herein byreference.

As the energy active ray-curable resin to be used as resin B, anyappropriate energy active ray-curable resin can be used. Examples ofenergy active ray-curable resins include photocurable resins, typicallyUV-curable resins. Specific examples of UV-curable resins includevarious resins such as polyester-based, acrylic, urethane-based,amide-based, silicone-based, and epoxy-based resins. These includeUV-curable monomers, oligomers, polymers and the like. These resins maybe used each alone by itself, or in combination (e.g., blending,copolymerization) of a plurality of these resins. Preferably, it is anacrylic resin. The UV-curable acrylic resin includes a monomer componentand an oligomer component having preferably two or more, and morepreferably three to six, UV-polymerizing functional groups. Specificexamples of UV-curable acrylic resins include epoxy acrylate, polyesteracrylate, acrylic acrylate, and ether acrylate. Typically, aphotopolymerization initiator is mixed in the UV-curable resin. Thecuring method may be a radical polymerization method or a cationicpolymerization method. Since the photocurable resin before curingcontains a large amount of monomer components, it offers high ease ofapplication, resulting in the formation of high-precision patterns. Notethat the energy active ray-curable resin to be used as resin B may be anenergy active ray-curable resin that is used as an adhesive, and theenergy active ray-curable resin composition for forming resin B may bean adhesive composition.

In the present invention, the shape, dimensions of the shape, densitywithin the plane of the first layer, and occupancy in the first layer ofthe second regions are determined depending on the purpose andapplication for which the optical member according to the presentinvention is used. For example, in the case where good visibility, e.g.,transparency, is required in the aspect in which the optical memberaccording to the present invention is employed, the major axis of theshape of each second region is preferably 100 μm or less, and morepreferably 70 μm or less. More specifically, in the case where theplurality of second regions have a pattern of multiple circles as shownin FIG. 7, the diameter of the each circular second region is preferably100 μm or less. By adopting such dimensions, when a person observes adevice incorporating the optical member according to the presentinvention at a relatively close distance, as in a mobile display,small-sized signage, etc., the person can be prevented from visuallyrecognizing the second regions. Moreover, the dimensions of one secondregion, density of the second regions within the plane of the firstlayer (number of regions/cm²), and the areal occupancy of the secondregions may be designed in accordance with the quantity of light that isrequired in the aspect in which the optical member according to thepresent invention is employed. The geometric pattern of second regionsin the plane of the first layer may be selected arbitrarily from amonguniform, local, random, or other patterns, depending on the purpose andapplication. Alternatively, the geometric pattern may be such that, asshown in FIG. 6 and FIG. 7, the second regions are first sparse andlater become denser away from the light source.

In the present invention, the second regions may extend from the firstmain surface over to the second main surface of the first layer so as tobe contiguous with the first region. As in the aforementioned example,the second regions are defined by filled regions, in which the pores inthe first region having a pore structure are filled with a resin orother substance. This improves adhesion between the first layer and thesecond layer provided on the first main surface of the first layer oranother member that may be provided on the second main surface of firstlayer, and realizes excellent mechanical strength. In particular, in thecase where the resin or other substance used for filling is apressure-sensitive adhesive or the like, mechanical strength of thefirst layer can be improved more significantly. Moreover, when the firstlayer is configured so that the second regions extend from the firstmain surface over to the second main surface of the first layer so as tobe contiguous with the first region, unintended formation of air layersbetween the first region and the second regions can be prevented,whereby light scattering can be suppressed.

Specific examples of the method of forming the second regions accordingto the present invention will be described in detail at <3. Method ofproducing optical member>.

2-D. Second Layer

The optical member according to the present invention includes a secondlayer having a refractive index n₂. In the present invention, althoughthe second layer may be composed of any suitable material without beingparticularly limited, it is preferably formed so that n₂ is 1.43 ormore. The lower limit value of n₂ is usually 1.43 or more, andpreferably 1.47 or more. On the other hand, the upper limit of n₂ isusually 1.7 or less, although not particularly limited. When theaforementioned distribution element has the first layer, the secondlayer, and the lightguide integrated in this order, the refractive index(n₂) of the second layer is desirably equal to the refractive index ofthe lightguide, or is a close enough refractive index not to exert anyoptical influences, from optical standpoints.

As for the thickness of the second layer, although it is notparticularly limited so long sufficient strength for supporting thefirst layer is provided, its lower limit value is usually 1 μm or more,preferably 5 μm or more, and more preferably 10 μm or more, and itsupper limit value is usually 200 μm or less, and preferably 150 μm orless.

In the present invention, the second layer may be composed of resin A.Examples of a second layer composed of resin A includepressure-sensitive adhesive layer A, a substrate material layer, and thelike. Pressure-sensitive adhesive a, as resin A, is preferably suchthat: under normal temperature and pressure conditions under heatingconditions such as the aging step to be described later,pressure-sensitive adhesive a has a sufficient storage modulus ofelasticity not to permeate the pores in the first region; and the stateof pressure-sensitive adhesive a is able to appropriately change withlaser irradiation. From these standpoints, the storage modulus ofelasticity of pressure-sensitive adhesive a has an lower limit valuewhich is preferably 1.0×10⁵ (Pa) or more, and more preferably 1.2×10⁵(Pa) or more, and an upper limit value which is 1.0×10⁶ (Pa) or less.

As pressure-sensitive adhesive a, any appropriate pressure-sensitiveadhesive can be used so long as it has the aforementionedcharacteristics. Examples of pressure sensitive adhesives typicallyinclude acrylic pressure-sensitive adhesives (acrylic pressure-sensitiveadhesive compositions). An acrylic pressure-sensitive adhesivecomposition typically contains a (meth)acrylic polymer as a maincomponent (base polymer). The (meth)acrylic polymer may be contained inthe pressure-sensitive adhesive composition at a rate of e.g. 50 wt % ormore, preferably 70 wt % or more, and more preferably 90 wt % or more,of the solids content of the pressure-sensitive adhesive composition. Asthe monomer unit, the (meth)acrylic polymer contains alkyl(meth)acrylate as a main component. Herein, (meth)acrylate refers toacrylate and/or methacrylate. An example of the alkyl group of the alkyl(meth)acrylate may be a linear or branched-chain alkyl group having 1 to18 carbon atoms. The average number of carbon atoms in the alkyl groupis preferably from 3 to 9. Other than alkyl (meth)acrylate, the monomerto compose the (meth)acrylic polymer may include a carboxylgroup-containing monomer, a hydroxyl group-containing monomer, an amidegroup-containing monomer, an aromatic ring-containing (meth)acrylate, aheterocyclic ring-containing (meth)acrylate, and other comonomers. Thecomonomers are preferably hydroxyl group-containing monomers and/orheterocyclic ring-containing (meth)acrylates, and more preferablyN-acryloyl morpholine. The acrylic pressure-sensitive adhesivecomposition can preferably contain a silane coupling agent and/or across-linking agent. An example of the silane coupling agent may be asilane coupling agent containing an epoxy group. Examples of thecross-linking agent include isocyanate-based cross-linking agents andperoxide-based cross-linking agents. Details of such pressure-sensitiveadhesive layers or acrylic pressure-sensitive adhesive compositions aredescribed, for example, in Japanese Patent No. 4140736, the disclosureof which is incorporated herein by reference.

The substrate material layer composed of resin A may be an opticallytransparent resin film, and a typical example thereof may be a film inwhich a thermoplastic resin or a reactive resin (e.g., an ionizingradiation-curable resin) is used. Specific examples of thermoplasticresins include (meth)acrylic resins such as polymethyl methacrylate(PMMA) and polyacrylonitrile, polycarbonate (PC) resins, polyesterresins such as PET, cellulose-based resins such as triacetyl cellulose(TAC), cyclic polyolefin-based resins, and styrene-based resins.Specific examples of ionizing radiation-curable resins include epoxyacrylate-based resins and urethane acrylate-based resins. These resinsmay each be used alone by itself, or any two or more of them may be usedin combination.

3. Method of Producing Optical Member

Hereinafter, a novel method of producing an optical member according tothe present invention will be described in detail. So long as an opticalmember satisfying the relationship n₁<n₃<n₂ expressed by inequality (1)above is obtained, the method is not limited to the following aspect.

3-A. Laser Irradiation

As a method of producing an optical member according to the presentinvention, a production method using laser irradiation will describedbelow.

Specifically, as shown in FIG. 11, it is a method in which a precursorof the first layer is formed by using the first region 101; the secondlayer 200 is provided on a first main surface the precursor of the firstlayer; a main surface of the second layer 200 not having the first layeris irradiated with laser light 9 in a predetermined pattern, whereby thesubstance composing the second layer 200 melts and infiltrates the firstregion 101, thereby forming the second regions 102 (see the lower halfin FIG. 11). When the first region has a pore structure and the secondlayer contains resin A, resin A composing the second layer melts andinfiltrates the first region, whereby second regions are formed in whichthe substance composing the first region and resin A are contained ormixed. In this case, preferably, resin A composing the second layermelts and infiltrates the pores in the first region, and resin A fillsthe pores in the first region, thereby forming the second regions.

Hereinafter, with respect to an example case where resin A composing thesecond layer is pressure-sensitive adhesive A, a production method usinglaser irradiation will be described in more detail.

3-A-a. Formation of Precursor of First Region and First Layer

In the present invention, as described in detail (2-B. first region),the first region may have a pore structure. For example, the porestructure of the first region includes one type or a plurality of typesof structural units constituting fine pore structure, where thestructural units are chemically bonded to one another through catalyticaction. Example shapes of the aforementioned micropore structural unitinclude particle, fiber, rod, and fiat plate shapes. In the case wherethe micropore structural unit has a particle shape, the first region isformed of a pore structural body of porous material based on chemicalbonds between micropore particles. The structural unit may have only oneshape, or may have a combination of two or more shapes. Formation of theprecursor of the first region and the first layer will now be describedwith respect to an example case where the first region is a porestructural body of porous material based on chemical bonds betweenmicropore particles. As used herein, the precursor of the first layermeans a layer that substantially comprises the first region.

The method of forming the first region serving as the precursor of thefirst layer typically includes: a precursor formation step of forming,on a resin film or a lightguide, a precursor of a layer comprising thefirst region (e.g., a precursor of the aforementioned pore structuralbody of porous material based on chemical bonds between microporeparticles); and a cross-linking reaction step of causing a cross-linkingreaction inside the precursor after the precursor formation step Themethod further includes a particle-containing liquid producing step ofproducing a particle-containing liquid containing micropore particles(hereinafter, a “micropore particle-containing liquid” or simplyreferred to as a “particle-containing liquid”) and a drying step ofdrying the particle-containing liquid, where the precursor formationstep causes the micropore particles within the dried body to becomechemically bonded to one another to form the precursor. Theparticle-containing liquid is not particularly limited, but may be asuspension containing micropore particles, for example. In the presentinvention, it is preferable that the micropore particles are pulverizedmatter of a gel-like compound, and it is more preferable that thegel-like compound is a gel-like silicon compound. In this case, thefirst region is porous silicone.

Through the particle-containing liquid producing step of producing aparticle-containing liquid containing micropore particles (hereinafter,a “micropore particle-particle-containing liquid” or simply referred toas a “particle-containing liquid”), a liquid containing the microporeparticles (pulverized matter of a gel-like compound) (e.g., suspension)is produced. The micropore particle-containing liquid may be prepared bypreviously adding catalyst that allows micropore particles to bechemically bonded to one another. Moreover, the catalyst may be added tothe particle-containing liquid after the micropore particle-containingliquid has been prepared. The catalyst may be, for example, a catalystthat promotes cross-linking between the micropore particles. As achemical reaction to chemically bond the micropore particles to oneanother, when the micropore particles are pulverized matter of agel-like silicon compound, it is preferable to use thedehydration-condensation reaction of the residual silanol groups in thesilica sol molecules. By promoting the reaction between the hydroxylgroups of the silanol groups with a catalyst, a continuous filmformation that cures the pore structure in a short time is possible.Examples of catalysts include photoactive catalysts and thermally activecatalysts.

With a photoactive catalyst, for example, in a precursor formation stepof forming a precursor of a layer comprising the first region, microporeparticles can be chemically bonded to one another (e.g. cross-linked)without heating. As a result, in the precursor formation step, forexample, shrinking of the entire precursor is unlikely to occur, wherebya higher porosity can be maintained. In addition to or instead of acatalyst, a substance that generates a catalyst (catalyst generatingagent) may be used. For example, in addition to or instead of aphotoactive catalyst, a substance that generates a catalyst with light(a photocatalyst generating agent) may be used; or, in addition to orinstead of a thermally active catalyst, a substance that generates acatalyst with heat (a thermal catalyst generating agent) may be used.Examples of photocatalyst generating agents include photo-basegenerating agents (i.e., substances than generate basic catalysts withlight irradiation), photo-acid generating agents (i.e., substances thatgenerate acidic catalysts with light irradiation), and the like, wherephoto-base generating agents are preferable.

Next, for example, a resin film or a lightguide is coated with aparticle-containing liquid (e.g., a suspension) containing the microporeparticles (coating process). Various suitable coating methods can beused for the coating. A coating film containing the micropore particlesand the catalyst can be formed by applying the particle-containingliquid containing the micropore particles (e.g., pulverized matter of agel-like silicon compound) directly onto the resin film or thelightguide.

Next, through a drying step, the coating film that has been produced byapplying the micropore particle-containing liquid is dried, and anysolvent that was used in the particle-containing liquid, e.g., anorganic solvent, is volatized. The drying step may be, for example,natural drying, heat drying, or vacuum drying. Among others, in the casewhere industrial, continuous production is intended, heat drying ispreferably used. The method of heat drying is not particularly limited,and common means of heating can be used, for example. Examples of meansof heating include hot air blowers, heating rolls, far-infrared heaters,etc. The temperature of the drying treatment is e.g. 50° C. to 250° C.,preferably 60° C. to 150° C., and more preferably 70° C. to 130° C. Theduration of the drying treatment is e.g. 0.1 minutes to 30 minutes,preferably 0.2 minutes to 10 minutes, and more preferably 0.3 minutes to3 minutes. The solvent to be used for the particle-containing liquid ispreferably a solvent with low surface tension, for the purpose ofsuppressing compressive stress caused in the micropore particles due tosolvent volatization during drying, or occurrence of cracks in the porestructural body composed of porous silicone that may be caused bycompressive stress.

Next, through a cross-linking reaction step, micropore particles in thedried body of the coating film are allowed to be chemically bonded toone another. In the case where pulverized matter of a gel-like siliconcompound is used as the micropore particles, in the cross-linkingreaction step, for example, micropore particles are chemically bonded toone another through the action of a catalyst (basic substance). As aresult, for example, the three-dimensional structure of the pulverizedmatter in the dried body of the coating film becomes stabilized. In thecase of stabilizing the three-dimensional structure through conventionalsintering, a high temperature treatment at e.g. 200° C. or higher may beperformed, thereby inducing dehydration condensation of silanol groupsand formation of siloxane bonds. A cross-linking reaction in which aphotocatalyst generating agent is used to generate a catalyst todehydrate and condense the silanol groups is preferred because the porestructure can be formed and stabilized continuously without causingdamage to the resin film and at a relatively low drying temperaturearound 100° C. and in a short treatment time of less than severalminutes. Examples of photocatalyst generating agents include photo-basegenerating agents (substances that generate a basic catalyst by lightirradiation) and photo-acid generating agents (substances that generatesan acidic catalyst by light irradiation), where photo-base generatingagents are preferred.

A cross-linking reaction using a photocatalyst generating agent isperformed by light irradiation. The cumulative quantity of light throughlight irradiation, although not particularly limited, is e.g. 200 mJ/cm²to 800 mJ/cm²; preferably 250 mJ/cm² to 600 mJ/cm^(2,) and morepreferably 300 mJ/cm² to 400 mJ/cm², converted based on light havingwavelength of 360 cm. A cumulative quantity of light of 200 mJ/cm² ormore is preferable, from the standpoint of preventing an insufficientirradiation dose and inadequate decomposition by light absorption of thecatalyst and thus insufficient effects. From the standpoint ofpreventing the formation of thermal wrinkles due to damage to the resinfilm under the pore structural body, a cumulative quantity of light of800 mJ/cm² or less is preferable.

Next, a heating step, which is distinct from the drying step above, isperformed. The heating step is performed for the purpose of furtherpromoting cross-linking reaction inside the precursor after theaforementioned cross linking reaction step. Hereinafter, this heatingstep is referred to as an aging step. In the aging step, the heatingtemperature is set to a low temperature, and a cross-linking reaction isallowed to occur while suppressing shrinkage of the precursor. As aresult, the porosity in the layer comprising the first region, e.g., apore structural body of porous material based on chemical bonds betweenmicropore particles, is increased, and strength of the pore structuralbody can be improved. The temperature in the aging step is e.g. 40° C.to 70° C., preferably 45° C. to 65° C., and more preferably 50° C. to60° C. The duration of the aging step is e.g. 10 hr to 30 hr, preferably13 hr to 25 hr, and more preferably 15 hr to 20 hr.

For the sake of describing other embodiments below, the precursor afterthe cross-linking reaction step but before being subjected to the agingstep will be referred to as an aging step precursor.

Thus, a precursor of the layer substantially comprising the firstregion, the first layer, is obtained. Other than by the description inthe present specification, the method of producing the precursor of thefirst layer is also explained by the methods of producing a pore layeror a low-refractive index layer described in Japanese Laid-Open PatentPublication No. 2017-054111, Japanese Laid-Open Patent Publication No.2018-123233, and Japanese Laid-Open Patent Publication No. 2018-123299.

3-A-b. Formation of Second Layer

In a production method using laser irradiation, the second layer isprovided on the precursor of the first layer as obtained above. In thecase where the aforementioned precursor of the first layer is formed ona resin film or the like, the second layer is to be provided on a mainsurface of the aforementioned precursor of the first layer opposite toits surface on which the resin film is provided.

In the case where resin A composing the second layer ispressure-sensitive adhesive a, the second layer composed ofpressure-sensitive adhesive a is formed in advance on a separator, andthe second layer composed of pressure-sensitive adhesive a istransferred onto the precursor of the first layer, thereby allowing thesecond layer to be provided on the aforementioned precursor of the firstlayer.

As for resin A and the like for use in the second layer, see thedescription in (2-D. second layer).

3-A-c. Formation of Second Regions and First Layer

Hereinafter, a method (hereinafter referred to as the “laser irradiationmethod”) of producing an optical member by using laser irradiation willbe described, with respect to a case where the aforementioned precursorof the first layer is composed of a pore structural body of porousmaterial based on chemical bonds between micropore particles and thesecond layer is composed of pressure-sensitive adhesive a.

The laser irradiation method irradiates the second layer composed ofpressure-sensitive adhesive a (referred to as pressure-sensitiveadhesive layer A) with laser in a predetermined geometric pattern. As aresult, the state of pressure-sensitive adhesive a in thelaser-irradiated portion of pressure-sensitive adhesive layer changes,thereby making it easier for pressure-sensitive adhesive a to permeatethe pores in the precursor of the first layer. Pressure-sensitiveadhesive a fills the pores in the precursor of the first layer, wherebythe second regions are formed in the aforementioned predeterminedgeometric pattern, as a result of which the first layer is obtained. Aswill be described later, the second layer may be provided on an agingstep precursor, rather than on the aforementioned precursor of the firstlayer, and subjected to laser irradiation and then an aging step. In hiscase, the aging step, it is easier for pressure-sensitive adhesive a inthe laser-irradiated portion to permeate the pores in the aging stepprecursor.

Laser irradiation may be performed in any appropriate manner so long asthe state of pressure-sensitive adhesive a composing the second layer ischanged to make it easier for the pores in the precursor of the firstlayer to be permeated. The laser light used for laser irradiationincludes, usually, light of a wavelength of 100 nm or more as a lowerlimit, and light of a wavelength of 1900 nm or less as an upper limit.It includes preferably light of a wavelength of 300 nm to 1500 nm, morepreferably light of a wavelength of 300 nm to 1300 nm, and still morepreferably light of a wavelength of 500 nm to 1200 nm. In oneembodiment, the laser light has a Gaussian beam shape, and has a peekwavelength in the aforementioned ranges.

The laser light can be a nanosecond pulsed laser or a short pulsed laser(i.e., a laser that emits light with a pulse width of one nanosecond orless; for example, a picosecond laser or a femtosecond laser). Thefrequency of the laser light can be 50 kHz to 2000 kHz, for example.

Examples of lasers that emit laser light as described above include:solid-state lasers such as excimer lasers, YAG lasers, YLF lasers, YVO4lasers, and titanium-sapphire lasers; gas lasers including argon ionlasers, krypton ion lasers; fiber lasers; semiconductor lasers; dyelasers; SHG lasers which are YAG-based; and THG lasers which areYAG-based.

The laser irradiation can de performed, for example, by scanning(drawing) using CAD data. The manner (scan style) of laser irradiationcan be set as appropriate, depending on the purpose. The laser light raybe scanned in a straight line, for example, or in an S-shape, or in aspiral pattern, or a combination of these. A high-speed line scanner mayalso be used. As for the scan head, it may be a galvanometer scanner, apolygon scanner, or a combination of these.

The irradiation conditions of the laser light may be set to anyappropriate conditions. For example, when a solid-state laser (YAGlaser) is used, the output power is preferably 10 W to 20 W, and thepulse energy is preferably 10 μJ to 70 μJ. The scan speed is preferably10 mm second to 5000 mm second, and more preferably 100 mm second to2000 mm second. The scan pitch is preferably 10 μm to 50 μm. Theirradiated position of the laser light can be set on the surface of thesecond layer (i.e., the surface of pressure-sensitive adhesive layer A)or inside the thickness direction of pressure-sensitive adhesive layerA. At the laser irradiation stage, as shown in FIG. 11, a separator 6 isusually temporarily attached to the surface of pressure-sensitiveadhesive layer A. In this laser irradiation method, the irradiatedposition is set on the surface of pressure-sensitive adhesive layer A orinside the thickness direction of pressure-sensitive adhesive layer A(see the upper half in FIG. 11), whereby the state of pressure-sensitiveadhesive a of pressure-sensitive adhesive layer A can be changed for thebetter to allow the pores in the precursor of the first layer topermeate well, thus forming the second regions. The beam shape theirradiated position of the laser light can be set as appropriate,depending on the purpose. The beam shape may be a circle or line shape,for example. Any appropriate means of setting the beam shape to apredetermined shape may be employed. For example, the laser irradiationmay be performed through a mask having a predetermined aperture, or thebeam shaping may be performed by using a diffractive optical element orthe like. For example, if the beam shape is circular, the focal diameter(spot diameter) is preferably 50 μm to 60 μm. Furthermore, the inputenergy of the pulsed laser is preferably 20000 μJ/mm² to 100000 μJ/mm²,and more preferably 25000 μJ/mm² to 75000 μJ/mm². The input energyE(μJ/mm²) is derived from the following equation.

E=(e×M)/(V×p)

-   -   e: pulse energy (J)    -   M: repetition frequency (Hz)    -   V: scan speed (mm/sec)    -   p: scan pitch (mm)

The laser irradiation may preferably be performed in the same step asthe aging step for obtaining the precursor of the first layer. Byperforming the laser irradiation and the aging step concurrently,pressure-sensitive adhesive a is allowed to efficiently permeate thepores in the precursor of the first layer, thus forming the first layerwith the second regions formed therein.

(3-B. Ink Jet Technique I)

As a method of producing an optical member according to the presentinvention, a production method urine ink jet technique will be describedbelow.

Specifically, a method of producing an optical member by ink jettechnique converts a resin or other substance into ink, and by an inkjet, fills the pores in the aforementioned precursor of the first layerwith the ink in a predetermined geometric pattern, thereby forming thesecond regions. Alternatively, the pores in the aforementioned agingstep precursor are filled with the ink in a predetermined geometricpattern, and the aforementioned aging step is performed to form thesecond regions. The filling with the ink may be done directly to thepores. Alternatively, it may be done through: a step of leaving a resinor other substance that is provided in a predetermined geometric patternon the aforementioned precursor of the first layer or aging precursorunder normal temperature and pressure, etc., conditions, to causenatural infiltration and filling; or a heating step a such as an agingstep to induce softening, thus causing infiltration and filling. Herein,the aforementioned precursor of the first layer and aging step precursorare as described in (3-A-a. formation of precursor of first region andfirst layer).

In an ink jet technique, the resin being contained in the second regionsmay be identical to resin A composing the second layer, or may be resinB that is different from resin A. Resin A and resin B have beendescribed in (2-C. second regions) and (2-D. second layer). Resin A hasdifficulty in infiltrating the pores in the aforementioned precursor ofthe first layer or the like under normal temperature and pressure andheating conditions (e.g., aging step); on the other hand, resin B or aresin B composition easily infiltrates the pores in the aforementionedprecursor of the first layer or the like under normal temperature andpressure and heating conditions (e.g., aging step).

In any of the ink jet techniques described below, the ink diameter andthe ink jetting method may be selected in any appropriate mannerdepending on the shape of the second regions to be formed and the sizeof the shape.

Hereinafter, with respect to an example case where resin A composing thesecond layer is pressure-sensitive adhesive a, and resin B contained inthe second regions is pressure-sensitive adhesive b, an example (ink jettechnique I) of a production method using ink jet technique will bedescribed in more detail.

As shown in FIG. 12, on the surface of a pressure-sensitive adhesivelayer as the second layer 200, this ink jet technique I forms apredetermined geometric pattern by using, pressure-sensitive adhesive b(201 a), thus preparing a pressure-sensitive adhesive laminate bodyincluding a resin B pattern layer 201. The surface of thepressure-sensitive adhesive laminate body having the resin B patternlayer 201 thereon is disposed so as to adjoin the first main surface ofthe aforementioned precursor of the first layer or the aging stepprecursor, and then pressure-sensitive adhesive b to compose the resin Bpattern layer is allowed to infiltrate the pores in the aforementionedprecursor of the first layer or the aging step precursor through aheating step such as an aging step. As a result, a first layer isobtained in which second regions 102 are formed in a predeterminedgeometric pattern, containing pressure-sensitive adhesive b and thesubstance composing the first region 101 (see the lower half in FIG.12).

Formation of the geometric pattern of the resin B pattern layer can beachieved by any appropriate means. In one embodiment, the resin Bpattern layer may be formed by attaching the cured (i.e., in a usualstate) pressure-sensitive adhesive b, in a predetermined pattern,together with pressure-sensitive adhesive layer A. This embodiment iseasy and useful in the case where the geometric pattern is stripe- orlattice-shaped, for example. In another embodiment, the resin B patternlayer can be formed in a predetermined geometric pattern by convertingthe uncured pressure-sensitive composition (pressure-sensitive adhesiveb coating liquid) into ink, and printing it via ink-jet and curing it.In this case, a weight-average molecular weight Mw of the base polymerwithin the pressure-sensitive adhesive b composition is preferably2000000 or less, and more preferably 5000 to 1600000. When Mw of thebase polymer is in such ranges, high-precision pattern formation becomespossible. In still another embodiment, the resin B pattern lever can beformed by applying the uncured pressure-sensitive adhesive b composition(pressure-sensitive adhesive b coating liquid) onto pressure-sensitiveadhesive layer A, i.e., the second layer via a mask having apredetermined geometric pattern.

Next, the pressure-sensitive adhesive laminate body of pressuresensitive adhesive layer A/resin B pattern layer having a predeterminedgeometric pattern is attached together with the precursor of the firstlayer or the like, in such a manner that the resin B pattern layerhaving the predetermined geometric pattern adjoins the first mainsurface of the precursor of the first layer. Since pressure-sensitiveadhesive b in the resin B pattern layer is able to permeate the pores inthe precursor of the first layer or the like as it is, a first layerhaving second regions disposed in the predetermined geometric pattern isobtained. When of the first layer, the attaching-together of thepressure-sensitive adhesive laminate body with the aging precursor ispreferably followed by an aging step. With such configuration,infiltration of pressure-sensitive adhesive b into the pores in theaging precursor can be promoted by the aging step.

3-c. Ink Jet Technique II

Hereinafter, with respect to an example case where resin A composing thesecond layer is pressure-sensitive adhesive a and resin B contained inthe second regions 102 is an energy active ray-curable resin, anotherexample (ink jet technique II) of a production method using ink jettechnique will be described in more detail.

As shown in FIG. 12, on the surface of pressure-sensitive adhesive layerA as the second layer 200, this ink jet technique II forms predeterminedgeometric pattern by using an energy active ray-curable resincomposition 201 a, thus preparing a curable resin composition laminatebody including a curable resin pattern layer 201. The surface of thecurable resin composition laminate body having the curable resin patternlayer 201 thereon is disposed so as to adjoin the first main surface ofthe aforementioned precursor of the first layer or the aging stepprecursor, and then, through a heating step such as an aging step, anenergy active ray-curable resin composition to compose the curable resinpattern layer is allowed to infiltrate the pores in the aforementionedprecursor of the first layer or the aging step precursor, and irradiatedwith an energy active ray to become an energy active ray-curable resin.As a result, a first layer is obtained in which second regions areformed in a predetermined geometric pattern, containing the energyactive ray-curable resin and the substance composing the first region101 (see the lower half in FIG. 12). In this ink jet technique II, it ispreferable that: the curable resin composition laminate body having thecurable resin pattern layer is disposed so as to adjoin the aging stepprecursor; the energy active ray-curable resin composition is allowed toinfiltrate the pores in the aforementioned aging step precursor; curingwith energy active ray irradiation is performed; and then an aging stepis performed.

This ink jet technique II applies the uncured photocurable resin(photocurable resin composition) in a predetermined geometric patternonto the surface of pressure-sensitive adhesive layer A, for example,disposes the photocurable resin composition so as to adjoin theaforementioned precursor of the first layer or the like, allows thephotocurable resin composition to permeate the pores in theaforementioned precursor of the first layer or the like, and photocuresit. As a result, the second regions 102 are formed in the predeterminedgeometric pattern, whereby the first layer is obtained.

Examples of pressure-sensitive adhesive a composing pressure-sensitiveadhesive layer A, i.e., the second layer, may be those mentioned in(2-C. second regions). By using any such pressure-sensitive adhesive a,pressure-sensitive adhesive a is prevented from permeating any unwantedportion other than the second regions, whereby the second regions can beprecisely obtained in the predetermined geometric pattern. Examples ofthe energy active ray-curable resin which is resin B may be the energyactive ray-curable resins mentioned in (2-D. second layer). As theenergy active ray-curable resin, photocurable resins such as UV-curableresins are preferable. Hereinafter, photocurable resins described asexamples.

In one aspect of this ink jet technique II, the photocurable resin maybe converted into ink, and applied via ink-jet in a predeterminedpattern. As described in (2-D. second layer) above, the uncuredphotocurable resin profusely contains monomer components, and thus iseasily converted into ink, and allows itself to be easily applied,thereby enabling high-precision pattern formation. In another aspect,the photocurable resin may be applied to pressure-sensitive adhesivelayer through mask having a predetermined geometric pattern.

Next, the photocurable resin composition laminate body includingpressure-sensitive adhesive layer A/photocurable resin pattern layer isattached together so that the photocurable resin adjoins the first mainsurface of the precursor of the first layer or the aging step precursor.The attaching-together of the photocurable resin composition laminatebody is preferably performed for the aging step precursor. The curing ofthe photocurable resin (light irradiation) also preferably performedbefore the aging step. By performing the curing (light irradiation)before the aging step, unwanted diffusion of the photocurable resincomposition (which is substantially a monomer) in the aging stepprecursor can be suppressed, whereby the second regions can be preciselyformed in the predetermined geometric pattern. Specifically, the curing(light irradiation) may be performed after the attaching-together of thephotocurable resin composition laminate body with the aging stepprecursor and before the aging step.

Since the photocurable resin applied on pressure-sensitive adhesivelayer A has some ability to maintain shape as it is (i.e., without beingcured), performing the curing (light irradiation) after theattaching-together (and before the aging step) presents no substantialproblem. In this manner, the photocurable resin is allowed to fill thepores in the aging step precursor through infiltration and lightirradiation and the aging step are performed in this order, whereby afirst layer including the first region and the second regions formed inthe predetermined geometric pattern is obtained.

4. Other Light Distribution Elements 4-A. Modifications of LightDistribution Element

Modifications of the light distribution element described in <1. Lightdistribution element> above will be explained. In a light distributionelement shown in FIG. 8, an optical member according to the presentinvention is disposed so that the second main surface of the secondlayer is in contact with a first main surface of a lightguide 4. In thecase of the light distribution element shown in FIG. 8, as described in(2-D. second layer), the refractive index (n₂) of the second layer ispreferably equal to the refractive index of the lightguide or a closeenough refractive index not to exert any optical influences, fromoptical standpoints.

In a light distribution element shown in FIG. 9 a resin film 7 isdisposed in contact with the second main surface of the first layer 100of an optical member according to the present invention and with a firstmain surface 41 of a lightguide 4. The lightguide 4 and the resin film 7may be attached together via an adhesive or the like. The resin film 7may be an optically transparent resin film similar to the substratematerial layer described in (2-D. second layer). As the resin film 7,the resin film which is to be coated with a precursor of a porestructural body of porous material based on chemical bonds betweenmicropore particles as described in <3. Method of producing opticalmember> above may be straightforwardly used. The refractive index of theresin film 7 is preferably equal to the refractive index of thelightguide or a close enough refractive index not to exert any opticalinfluences, from optical standpoints.

4-B. Light Distribution Element in which a Light Extraction Layer havingCavities (a Member having Air Cavity Pattern Structure to Achieve LightOut-Coupling) is Used

FIG. 10 shows a light distribution element that includes a light wide 4,an optical member according to the present invention, and a lightextraction layer 8 having cavities. The cavities may also be referred toas air cavities. Specifically, in the light distribution element, theoptical member according to the present invention is provided on thenon-patterned light extraction side of the lightguide 4 in such a mannerthat the first layer 100 is in contact therewith, and the lightextraction layer 8 having cavities (air cavities 801) is disposed on thesecond layer 200. In this configuration, light which enters thelightguide 4 from the light source propagates while undergoing totalreflection between the bottom surface of the lightguide 4 and the firstregion 101 of the first layer 100, and light transmitted through thesecond regions 102 is refracted toward the light extraction side by thelight extraction layer 8 having cavities. As a result, light extractionefficiency can be improved, with a uniform luminance distribution.

The light extraction layer 8 having cavities includes an optical cavitypattern that is embedded within the resin layer, the cavity patternhaving the function of refracting light. The light extraction layerhaving cavities may also be referred to as a member having an air cavitypattern structure to achieve light out-coupling. The light extractionlayer having cavities can be made of resin, a glass film, or the like.FIG. 13 shows a method of producing the light extraction layer havingcavities. FIG. 13 illustrates a lamination method that is adhesive-free.A non-patterned first film 812 and a second film 811 having a desiredpattern formed on its surface are attached in an adhesive-free manner(e.g. through microwave surface treatment). The first film 812 and thesecond film 811 are made of polymethyl methacrylate (PMMA),polycarbonate (PC), or the like. Through the attaching-together, the aircavities 801 are formed.

Another method of producing the light extraction layer having cavitiesmay be a method which adhesively bonds two films by using an adhesionlayer. The cohesion layer may have a thickness of about 1 to 3 μm. Asthe second film 811 and the first film 812 are attached together via theadhesion layer, the air cavities 801 are formed. During theattaching-together, it is ensured chat the pre-cured adhesive does notgo into the cavity pattern. The method of attaching together may be anymethod that does not affect the shape of the air cavities. For example,the laminate surface may be pretreated with a VUV light (vacuumultraviolet) source or an APP (atmospheric plasma) and then laminatedunder constant pressure, whereby a chemical bond can be obtained. Thismethod can achieve good mechanical strength.

INDUSTRIAL APPLICABILITY

An optical member according to the present invention may be combinedwith a lightguide or the like into a light distribution element, beingapplicable to frontlights, backlights, window/facade illumination,signage, signal illumination, solar applications, decorativeillumination, light shields, light masks, roof lighting, or other publicor general illumination. For example, an optical member according to thepresent invention is suitably used as a component element of afrontlight in a reflection type display, which is an example of signage.Using an optical member according to the present invention allows animage or graphic on a reflection type display to be observed withoutvisible blur or other optical disadvantages that may be caused byscattered diffracted light.

Example

Hereinafter, the present invention will be specifically described by wayof Examples; however, the present invention is not to be limited toExamples. The method of measuring each property is as follows.

(1) Measurement of Refractive Index

After a first layer was formed on an acrylic film, it was cut into a 50mm×50 mm size, and via a pressure-sensitive adhesive layer, the firstlayer was attached onto the surface of a glass pate (thickness: 3 mm).The central portion of the rear surface of the glass plate (diameter:about 20 mm) was thoroughly painted with a black marker, therebyproviding a sample in which would not occur at the rear surface of theglass plate. The above sample was set in an ellipsometer (VASE:manufactured by J.A. Woollam Japan, Inc.), and its refractive index wasmeasured at a wavelength of 500 nm and an angle of incidence of 50 to 80degrees.

(2) Effects of Light Extraction

Via an acrylic pressure-sensitive adhesive (refractive index 1.47,thickness 5 μm), an optical member obtained according to Example 1 belowwas attached to a resin plate (manufactured by Mitsubishi ChemicalCorporation, “Acrylite EX001”) having a thickness of 2 mm. Light wasallowed to enter at an end of the plate, and the state of lightdistribution was confirmed visually and with a microscope.

[Manufacturing Example 1] Preparation of Coating Liquid (MicroporeParticle-Containing Liquid) for Forming First Region, and Production ofAging Step Precursor Film (1) Gelation of Silicon Compound

Mixed solution A was prepared by dissolving 0.95 g ofmethyltrimethoxysilane (MIMS), i.e., a precursor of a silicon compound,in 2.2 g of dimethyl sulfoxide (DMSO). To this mixed solution A, 0.5 gof 0.01 mol/L acid aqueous solution was added and stirred for 30 minutesat room temperature to hydrolyze the MIMS, thereby producing mixedsolution B containing tris(hydroxy)methylsilane.

To 5.5 g of DMSO, 0.28 g of 28 wt % ammonia water and 0.2 g of purewater were added, and then the aforementioned mixed solution B wasfurther added and stirred for 15 minutes at room temperature to gelatethe tris(hydroxy)methylsilane, thereby providing mixed solution Ccontaining the gel-like silicon compound.

(2) Aging Treatment

Mixed solution as prepared above, containing the gel-like siliconcompound, was incubated at 40° C. for 20 hours as it was, thus carryingout an aging treatment.

(3) Pulverization Treatment

Next, the gel-like silicon compound, which had been subjected to agingtreatment as above, was crushed using a spatula into granules of severalmm to several cm in size. Then, 40 g of isopropyl alcohol (IPA) wasadded to mixed solution C. The mixture was gently stirred and left atroom temperature for 6 hours, for decantation of the solvent andcatalyst in the gel. The same decantation treatment was carried outthree times to achieve solvent replacement, thereby providing mixedsolution D. Then, the gel-like silicon compound in the mixed solution Dwas pulverized (high media-less pulverization. As for the pulverizationtreatment (high pressure media-lass pulverization), 1.85 g of thegel-like compound and 1.15 g of IPA in mixed solution D were weighedinto a 5 cc screw bottle, and thereafter these was pulverized under theconditions of 50 W, 20 kHz for 2 minutes by using a homogenizer (S.M.T.Co. Ltd., product name. “UH-50”).

Through the pulverization treatment, the gel-like silicon compound inthe aforementioned mixed solution was pulverized, which resulted inmixed solution D′being a sol liquid of the pulverized matter. The volumeaverage particle size, which indicates the particle size variation ofthe pulverized matter contained in mixed solution D′, was confirmed tobe 0.50 to 0.70 by a dynamic light-scattering nanotrack particle sizeanalyzer (type UPA-EX150 manufactured by Nikkiso Co., Ltd.).Furthermore, to 0.75 g of this sol liquid (mixed solution C′), 0.062 gof a 1.5 wt % MEK (methyl ethyl ketone) solution of a photo-basegenerating agent (Wako Pure Chemical Industries, Ltd.: product nameWPBG266) and 0.036 g of a 5% MEK solution of bis(trimethoxysilyl)ethanewere added at these respective ratios, thus providing a coating liquidfor first region formation (micropore particle-containing liquid).

A coating film was formed by applying (coating) the above coating liquidonto the surface of an acrylic resin film (thickness: 40 μm) which wasprepared according to Manufacturing Example 1 in Japanese Laid-OpenPatent Publication No. 2012-234163. The coating was treated at atemperature of 100° C. for 1 minute and then dried, and the driedcoating film was further irradiated with UV for an amount of lightirradiation (energy) of 300 mJ/cm² using light having a wavelength of360 nm, thereby providing a laminate body (an acrylic film with a porestructural layer), having the first region serving as the precursor ofthe first layer (a pore structural body of porous material based onchemical bonds between micropore particles) formed on the aforementionedacrylic resin film. The pore structural layer had a refractive index of1.15.

Example 1

An acrylic pressure-sensitive adhesive (thickness 10 μm, refractiveindex 1.47) was formed on mold-release treated PET (polyethyleneterephthalate). A mixed solution of an epoxy-based monomer adjusted to aconcentration of 25% was dropped as ink on a 30 mm×50 mm region of theacrylic pressure-sensitive adhesive, at a 10 mm pitch and in a geometricpattern similar to that in FIG. 7, using “PIJIL-HV inkjet apparatus fromCluster Technology Co., Ltd.”. To facilitate observation under amicroscope, a small amount of visible light-absorbing dye was added tothe mixed solution, thus resulting in a separate mixed solution beingproduced as the mixed solution for observation. The size of the mixedsolution for observation after dropping was observed under a microscope,which indicated that the diameter of one of the regions constituting thegeometric pattern formed on they pressure-sensitive adhesive layer was66 μm, as shown in FIG. 14. After the aforementioned mixed solution wasdropped, the pressure-sensitive adhesive having undergone theaforementioned ink treatment was attached together with the porestructural layer having a refractive index 1.15 prepared as above.Thereafter, the pressure-sensitive adhesive layer-pore structural layerlaminate body was irradiated with UV light from the pore structural bodyside, for an irradiation dose of 600 mJ. Then, it was stored in a dryingmachine at 60° C. for 20 hours, whereby an optical member having a firstlayer including the second regions was obtained.

Now, in order to confirm the refractive index of the second regionsafter 24 hours at 60° C. as above, a sample of a layer consisting onlyof the second regions was obtained separately, in a similar matter tothe above but without forming geometric pattern and with dropping theaforementioned mixed solution over the entire surface of the porestructural layer in a range of 50 mm×50 mm. This sample was measured toshow a refractive index of 1.35.

The film of the first layer above was attached together with an acrylicplate with a thickness of 2 mm and observed under a microscope whileallowing light to enter at an end, whereby it was confirmed that lightwas being transmitted only through the inked regions (the secondregions). The size of the circular second regions was 68 μm in diameter.From the above, it was found that n₁ and n₂ were respectively 1.15 and1.47 in the resultant optical, member, and n₃ was inferred to be 1.35,given the fact that light was being transmitted.

Comparative Example 1

In Manufacturing Example 1, when coating the acrylic resin film with thecoating liquid (micropore particle-containing liquid), a mask patternmay be disposed on the acrylic resin film before applying the coatingliquid, and otherwise through a similar manner, a pore structural layerin which a pore structural body in accordance with the mask pattern ispartially formed can be formed. By attaching this patterned porestructural layer together with an acrylic pressure-sensitive adhesive(thickness of 10 μm, refractive index 1.47), an optical member having alight extraction layer similar to that of the prior-art document shownin FIG. 1 or FIG. 2 is obtained.

Confirming Leakage of Light With Calculation Software

By using Lighttools, optical effects of the present invention wereconfirmed by using optical members obtained according to Example 1 andComparative Example 1 as models. The calculation models were establishedsuch that, in a lightguide having an area of 90 mm×60 mm, a thickness of0.4 mm, and a refractive index 1.49, light would enter from theshorter-side end. On the lightguide, a first layer having a thickness of600 nm was added, in which a first region having a refractive index 1.15and dots of second regions having a size of 60 μm and a refractive indexof 1.35 were present. Next, on the first layer, a second layer having arefractive index of 1.47 and a thickness of 10 μm and a light extractionfilm having cavities as described in Japanese National Phase PCTLaid-Open Publication No. 2013-324288 were layered in this order, thusproviding a model corresponding to a light distribution element in whichExample 1 of the present invention as shown in FIG. 15 was used.Photodetecting portions were placed on the front and the rear of theaforementioned model, and quantities of light and distribution werecalculated. Except that the second regions had a refractive index of1.47 as shown in FIG. 16, similarly a model was establishedcorresponding to a light distribution element in which theaforementioned Comparative Example was used, and subjected tocalculation. The results are shown in Table 1.

TABLE 1 refractive refraction gradient index of between second regionsfirst region and rear (n₃) second regions illuminance Example 1 1.35 YES1491 Comparative 1.47 NO 2683 Example 1

FIG. 17 is a graph showing the quantity of leakage of light thecalculation models of Example 1 and Comparative Example 1 when tiltedfrom the center of the rear surface in the left and right polar angledirections. The line (n=1.35) represents the calculation model ofExample 1 and the dashed line (n=1.47) represents the calculation modelof Comparative Example 1. As can be seen from the graph, near polarangles of ±50 degrees, the calculation model of Example 1, correspondingto the present invention, is able to significantly suppress the quantityof light leaking compared to the calculation model of ComparativeExample 1.

From the above results, it can be seen that the refractive index havinggradient partly suppresses scattering, whereby leakage of light on therear surface side is suppressed.

Moreover, in Comparative Example 1, when once partially forming a porestructure, it is very difficult form a stable first layer, thus creatinga step when the second layer, e.g., a pressure-sensitive adhesive, isattached to ether, thus making it extremely difficult to obtain anoptically uniform and desired appearance.

REFERENCE SIGNS LIST

1 low-refractive index layer (nanopore layer)2 high-refractive index layer (pressure-sensitive adhesive layer)3 air layer4 lightguide41 first main surface of lightguide42 second main surface of lightguide5 light source100 first layer11 first main surface of first layer12 second main surface of first layer101 first region102 second region200 second layer201 resin B pattern layer201 a pressure-sensitive adhesive b (energy active ray-curable resincomposition)21 first main surface of second layer22 second main surface of second layer300 optical member according to the present invention6 separator7 resin film8 light extraction layer having cavities801 air cavity811 second film812 first film9 laser light

What is claimed is:
 1. An optical member comprising: a first layer thatincludes a first region having a refractive index n₁ and a second regionhaving a refractive index n₃, wherein the first region has a porestructure that does not comprise a resin; and a second layer disposed ona first main surface of the first layer so as to be in contact with thefirst region and the second region, the second layer having a refractiveindex n₂, wherein, the first layer includes a plurality of said secondregions adjoining the first region along a planar direction of the firstlayer; the plurality of second regions constitute a geometric pattern;and n₁ to n₃ satisfy inequality (1) below:n₁<n₃<n₂   (1).
 2. The optical member of claim 1, wherein, the secondlayer comprises resin A; and the second regions comprise a substancecomposing the pore structure and resin A.
 3. The optical member of claim1, wherein, the second layer comprises resin A; and the second regionscomprise a substance composing the pore structure and resin B.
 4. Theoptical member of claim 2, wherein the second regions are filled regionswhich are formed as a result of at least a portion of the pore structureof the first region being filled by resin A.
 5. The optical member ofclaim 3, wherein the second regions are filled regions which are formedas a result of at least a portion of the pore structure of the firstregion being filled by resin B.
 6. The optical member of claim 1,wherein the second regions may extend from the first main surface overto a second main surface of the first layer so as to be contiguous withthe first region.
 7. The optical member of claim 1, wherein n₁ is 1.2 orless and n₂ is 1.43 or more.
 8. The optical member of claim 2, whereinresin A is pressure-sensitive adhesive a.
 9. The optical member of claim3, wherein resin B is an energy active ray-curable resin.
 10. Theoptical member of claim 1, wherein, the first layer excluding the secondregions has a refractive index of 1.2 or less; the second layer has arefractive index of 1.43 or more; and the second regions have arefractive index which is not less than 1.25 and not more than 1.4. 11.A light distribution element comprising the optical member of claim 1and a lightguide.
 12. The light distribution element of claim 11,comprising a light extraction layer having cavities.